Liquid Crystal Display Device

ABSTRACT

In the step of curing a resin for bonding a TFT substrate and a counter substrate each having an alignment film that has been optically aligned by using UV-light, damage to the alignment film due to the UV-light can be prevented without using a light shielding mask. 
     A UV-light absorption layer is formed between each black matrix on the counter substrate. The TFT and counter substrates are sealed at their periphery by a resin that is cured by UV-light radiated from the counter substrate side. Since the absorption layer has a high absorbability to UV-light at a wavelength of 300 nm or less that degrades the alignment film, damage to the alignment film due to the UV-light for curing the resin can be prevented. Thus, provision of a light shielding mask for shielding the UV-light for the display region can be saved.

CLAIM OF PRIORITY

The present application claims priority from Japanese Patent ApplicationJP 2011-045502 filed on Mar. 2, 2011, the content of which is herebyincorporated by reference into this application.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal display device. Theinvention more particularly relates to a liquid crystal display deviceincluding an alignment film provided with alignment controllability byirradiation of light.

2. Description of the Related Art

Liquid crystal display devices include a TFT substrate having pixelelectrodes, thin film transistors (TFTs), etc. formed in a matrix; acounter substrate opposing the TFT substrate and having black matricesand an overcoat film, etc.; and liquid crystals put between the TFTsubstrate and the counter substrate. Images are formed by controllingthe light transmittance of the liquid crystal molecules of each pixel.

Since liquid crystal display devices are flat and light in weight, theyare applied in various fields, for example, from large-sized displaydevices such as television sets to mobile phones and DSCs (Digital StillCameras). For liquid crystal display devices, the view anglecharacteristic issues a problem. The view angle characteristic is aphenomenon such that the luminance or chromaticity changes from that ofwhen the screen is viewed from the front, when, the screen is viewedfrom an oblique direction. The IPS (In Plane Switching) system whichoperates liquid crystal molecules by a horizontal electric field has agood view angle characteristic.

As a method of alignment treatment, that is, a method for givingalignment controllability to an alignment film used for liquid crystaldisplay devices, rubbing treatment has been used in the conventionalart. Rubbing treatment is performed by rubbing an alignment film with acloth. On the other hand, there is a method called an optical alignmentmethod which can provide alignment controllability to an alignment filmin a contactless manner. Since the performance of the IPS system isbetter as the pre-tilt angle is smaller, the optical alignment methodwhich in principle does not generate a pre-tilt angle is advantageous.

The TFT substrate and the counter substrate are bonded at theirperiphery with a seal material; as the seal material, UV-curable resinis often used. When the display region in which the alignment film isformed is irradiated with UV-light to cure the seal material, theUV-light deteriorates the alignment film. Conventionally, a lightshielding mask has been used so that the display region is notirradiated with UV-light upon the UV-irradiation against the sealmaterial.

However, even when such a mask is used, the UV-light comes around todeteriorate the alignment film at the periphery of the display region.JP-A-H10-221700 discloses a configuration in which the counter substrateis provided with a band pass filter surrounding the outer side of thedisplay region so that it cuts off the UV-light, thereby protecting thealignment film and liquid crystals in the display region from theUV-light by the combination of the light shielding mask and the bandpass filter.

SUMMARY OF THE INVENTION

In a conventional configuration in which a light shielding mask isprovided to shroud the display region at the time the seal material iscured by UV-light irradiation, it is necessary to align the lightshielding mask to a predetermined position upon exposure. Thus,fabrication steps for this process would be added, and it is alsonecessary to prepare various sizes and kinds of light shielding masks.

Further, in a configuration as described in JP-A-H10-221700 in which thecounter substrate is provided with a band pass filter formed around theperiphery of the display region, there is an overlap between the bandpass filter and the seal material. The effect of the band pass filter onthe curing of the seal material needs to be taken into consideration. Itis also necessary matters such as the bondability between the band passfilter and the seal material as well as the black matrix, etc. aroundit. Further, even when the band pass filter is formed, a light shieldingmask will still be needed.

The present invention intends to attain a liquid crystal display deviceemploying an alignment film obtained by optical alignment and a UV-lightcurable resin for a seal material, which does not require the use of aUV-light shielding mask upon UV-curing of the seal material.

The present invention intends to overcome the problems described aboveand provides, in a first aspect, a liquid crystal display devicecomprising: a TFT substrate having an alignment film; a countersubstrate having an alignment film, the counter substrate being bondedto the TFT substrate by means of a seal material; and liquid crystalssealed inside the substrates and the seal material; wherein a UV-lightabsorption layer is formed between each black matrix, the black matricesand the UV-light absorption layer being covered by an overcoat film, theovercoat film being covered by the alignment film; the seal material isa UV-light curable resin; and the transmittance of the UV-lightabsorption layer to UV-light at a wavelength of 300 nm is lower thanthat of the overcoat film, and the transmittance of the UV-lightabsorption layer to UV-light at a wavelength of 340 nm is higher thanthat of the overcoat film.

The present invention provides, in a second aspect, a liquid crystaldisplay device comprising: a TFT substrate having an alignment film; acounter substrate having an alignment film, the counter substrate beingbonded to the TFT substrate by means of a seal material; and liquidcrystals sealed inside the substrates and the seal material; wherein aUV-light absorption layer is formed between each black matrix and overthe black matrices, and the alignment film is formed over the UV-lightabsorption layer; the TFT substrate is covered by a TFT circuit and anorganic passivation film covering the TFT circuit, and over the organicpassivation film, counter electrodes, an interlayer insulation film, andpixel electrodes are formed in that order, or in the order of the pixelelectrodes, the interlayer insulation film, and the counter electrodes;the alignment film is formed over the pixel electrodes or the countersubstrate; the seal material is a UV-light curable resin; and thetransmittance of the UV-light absorption layer to UV-light at awavelength of 300 nm is lower than that of the organic passivation film,and the transmittance of the UV-light absorption layer to UV-light at awavelength of 340 nm is higher than that of the organic passivationfilm.

The present invention provides, in a third aspect, a liquid crystaldisplay device comprising: a TFT substrate having an alignment film; acounter substrate having an alignment film, the counter substrate beingbonded to the TFT substrate by means of a seal material; and liquidcrystals sealed inside the substrates and the seal material; wherein acolor filter is formed between each black matrix, the black matrices andthe color filters being covered by an overcoat film, the overcoat filmbeing covered by the alignment film; the TFT substrate is covered by aTFT circuit and a UV-light absorption layer covering the TFT circuit,and over the UV-light absorption layer, counter electrodes, aninterlayer insulation film, and pixel electrodes are formed in thatorder, or in the order of the pixel electrodes, the interlayerinsulation film, and the counter electrodes; the alignment film isformed over the pixel electrodes or the counter substrate; the sealmaterial is a UV-curable resin; and the transmittance of the UV-lightabsorption layer to UV-light at a wavelength of 300 nm is lower thanthat of the overcoat film, and the transmittance of the UV-lightabsorption layer to UV-light at a wavelength of 340 nm is higher thanthat of the overcoat film.

The present invention provides, in a fourth aspect, a liquid crystaldisplay device comprising: a TFT substrate having an alignment film; acounter substrate having an alignment film, the counter substrate beingbonded to the TFT substrate by means of a seal material; and liquidcrystals sealed inside the substrates and the seal material; wherein aUV-light absorption layer is formed between each black matrix, the blackmatrices and the UV-light absorption layer being covered by an overcoatfilm, the overcoat film being covered by the alignment film; the TFTsubstrate is covered by a TFT circuit and a UV-light absorption layercovering the TFT circuit, and over the UV-light absorption layer,counter electrodes, an interlayer insulation film, and pixel electrodesare formed in that order, or in the order of the pixel electrodes, theinterlayer insulation film, and the counter electrodes; the alignmentfilm is formed over the pixel electrodes or the counter substrate; theseal material is a UV-curable resin; and the transmittance of theUV-light absorption layer to UV-light at a wavelength of 300 nm is lowerthan that of the overcoat film and that of the organic passivationlayer, and the transmittance of the UV-light absorption layer toUV-light at a wavelength of 340 nm is higher than that of the overcoatfilm and that of the organic passivation layer.

According to the present invention, the UV-light absorption layer thatabsorbs UV-light at a wavelength of 300 nm or less is formed in thedisplay region. Therefore, damaging to the alignment film by theUV-light can be prevented during the UV-irradiation for sealing the TFTsubstrate and the counter substrate having the alignment films by meansof the UV-light curable seal material. Since a light shielding mask forprotecting the display region against the UV-light radiated in theUV-irradiation step can be saved, the manufacturing cost of the liquidcrystal display device can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view of a liquid crystal display deviceaccording to Embodiment 1;

FIG. 2 is a manufacturing process of a liquid crystal display deviceaccording to the present invention;

FIG. 3 shows the UV-light transmission characteristic of a UV-lightabsorption layer relative to wavelength;

FIG. 4 is a table comparing the UV-light transmission characteristics ofthe liquid crystal display devices of Embodiment 1 and a conventionalexample;

FIG. 5 is a cross sectional view of a liquid crystal display deviceaccording to Embodiment 2;

FIG. 6 is a table comparing the UV-light transmission characteristics ofthe liquid crystal display devices of Embodiment 2 and 1 and theconventional example;

FIG. 7 is a cross sectional view of a liquid crystal display deviceaccording to Embodiment 3;

FIG. 8 is a cross sectional view of a liquid crystal display deviceaccording to Embodiment 4;

FIG. 9 is a cross sectional view of a display region of an IPS liquidcrystal display device;

FIG. 10 is a plan view showing an example of a pixel electrode of theIPS liquid crystal display device; and

FIG. 11 is a cross sectional view of the display region and the sealportion of the IPS liquid crystal display device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Prior to the explanation of the embodiments of the present invention,the configuration of an IPS liquid crystal display device to which thepresent invention is applied is described.

FIG. 9 is a cross sectional view showing a structure in a display regionof an IPS liquid crystal display device. The structure shown in FIG. 9is the structure generally used at present. In brief, a comb-teeth pixelelectrode 110 is formed over a counter electrode 108 formed in a solidcoated form with an insulation film 109 put between them. Liquid crystalmolecules 301 are rotated by the voltage between the pixel electrode 110and the counter electrode 108, and the light transmittance of the liquidcrystal layer 300 of each pixel is controlled to thereby form an image.

In FIG. 9, a gate electrode 101 is formed over a TFT substrate 100formed of glass. The gate electrode 101 is formed in the same layer asthe scanning line. The gate electrode 101 is formed from an AlNd alloyand a MoCr alloy stacked thereover.

A gate insulation film 102 of SiN is formed covering the gate electrode101. A semiconductor layer 103 of an a-Si film formed of is formed overthe gate insulation film 102 at a position opposing the gate electrode101. The a-Si film forms a channel portion of the TFT, and over the a-Sifilm, a drain electrode 104 and a source electrode 105 are formed withthe channel portion put between them. An n+Si layer (not shown) isformed between the a-Si film and the drain electrode 104 or the sourceelectrode 105. The n+Si layer is for establishing ohmic contact betweenthe semiconductor layer 103 and the drain electrode 104 or the sourceelectrode 105.

The drain electrode 104 also serves as a video signal line, and thesource electrode 105 is connected with the pixel electrode 110. Thedrain electrode 104 and the source electrode 105 are formedsimultaneously in the same layer. In this embodiment, the drainelectrode 104 or the source electrode 105 is formed of MoCr alloy. Whenit is desired to lower the electric resistance of the drain electrode104 or the source electrode 105, for example, an electrode structuresuch that an AlNd layer is put between MoCr alloys is used.

An inorganic passivation film 106 of SiN is formed to cover the TFT. Theinorganic passivation film 106 protects, particularly, the channelportion of the TFT against impurities. An organic passivation film 107is formed over the inorganic passivation film 106. Since the organicpassivation film 107 also has a function of planarizing the surface aswell as protecting the TFT, the film is formed thick. The thickness isfrom 1 μm to 4 μm.

A counter electrode 108 is formed over the organic passivation film 107.The counter electrode 108 is formed by sputtering ITO (Indium TinOxide), a transparent conductive film, over the entire display region.That is, the counter electrode 108 is formed in a planar form. After thecounter electrode 108 is formed over the entire surface by sputtering, aportion of the counter electrode 108 is removed by etching to form athrough hole 111 so as to establish conduction between the pixelelectrode 110 and the source electrode 105.

An interlayer insulation film 109 of SiN is formed covering the counterelectrode 108. After the interlayer insulation film 109 is formed, thethrough hole 111 is formed by etching. The through hole 111 is formed byetching the inorganic passivation film 106 using the interlayerinsulation film 109 as a resist.

Then, ITO which will be the pixel electrode 110 covering the interlayerinsulation film 109 and the through hole 111 is formed by sputtering.The pixel electrode 110 is formed by pattering the sputtered ITO. ITO asthe pixel electrode 110 is deposited in the through hole 111 as well.The source electrode 105 extending from the TFT and the pixel electrode110 are connected via the through hole 111 so that video signals aresupplied to the pixel electrode 110.

FIG. 10 shows an example of the pixel electrode 110. The pixel electrode110 is a comb-teeth electrode. Slits 112 are formed between thecomb-teeth. A planar counter electrode 108 is formed below the pixelelectrode 110 with an interlayer insulation film 109 not illustrated putbetween them.

When video signals are applied to the pixel electrode 110, liquidcrystal molecules 301 are rotated by the lines of electric forcegenerated between the pixel electrode 110 and the counter electrode 108through the slit 112. The light transmitting the liquid crystal layer300 is thus controlled, and thereby an image is formed.

Returning to FIG. 9, an alignment film 113 for aligning the liquidcrystal molecules 301 is formed over the pixel electrode 110. In FIG. 9,a counter substrate 200 is disposed with a liquid crystal layer 300 putbetween them. Since the device shown in FIG. 9 is a monochromatic liquidcrystal display device, a black matrix 201 and an overcoat film 202covering it are formed at the inner side of the counter substrate 200.

While the black matrix 201 is for improving the contrast, it alsofunctions as a light shielding film for the TFT. The overcoat film 202is formed to moderate the roughness of the surface. An alignment film113 for determining the initial orientation of the liquid crystals isformed over the overcoat film 202. The alignment film 113 of the countersubstrate side is also processed with an alignment treatment by opticalalignment in the same manner as for the alignment film 113 of the TFTsubstrate side.

Although not illustrated in FIG. 9, a columnar spacer made of resin isformed on the counter substrate side in order to define the gap betweenthe TFT substrate 100 and the counter substrate 200. Since the device ofFIG. 9 is a monochromatic liquid crystal display device, color filtersare not present. In color liquid crystal display devices, color filtersof colors such as red, green, blue, etc. are formed at both sides of theblack matrix 201.

FIG. 9 shows a configuration in which the counter electrode 108 isformed over the organic passivation film 107, and the comb-teeth pixelelectrode 110 is disposed thereover with the interlayer insulation film109 put between them. By contrast, there is also an IPS device of aconfiguration in which the pixel electrode 110 is disposed over theorganic passivation film 107, and a comb-teeth counter electrode 108 isdisposed thereover with the interlayer insulation film 109 put betweenthem. The present invention can be applied to either of the types ofIPS.

FIG. 11 is a cross sectional view of the display region and the sealportion of the IPS liquid crystal display device shown in FIG. 9employing optical alignment.

In FIG. 11, the part from the gate electrode 101 to the inorganicpassivation film 106 in FIG. 9 are collectively illustrated a TFTcircuit 120. In FIG. 11, the TFT circuit 120 is formed over a TFTsubstrate 100, an organic passivation film 107 is formed thereover, anda common electrode 108 painted in a solid form is formed over theorganic passivation film 107. A comb-teeth pixel electrode 110 is formedover the common electrode 108 with the interlayer insulation film 109put between them, and the pixel electrode 110 is covered by an alignmentfilm 113.

In FIG. 11, black matrices 201 are formed on a counter substrate 200. Anovercoat film 202 is formed to cover the black matrices 201, and analignment film 113 is formed over the overcoat film 202. Further, acolumnar spacer 130 is formed between the counter substrate 200 and theTFT substrate 100.

In FIG. 11, a seal material 150 is formed at the periphery of thecounter substrate 200 and the TFT substrate 100, and a liquid crystallayer 300 is sealed in the inner side of the seal material 150. In FIG.11, the seal material 150 is formed between the interlayer insulationfilm 109 of the TFT substrate 100 and the overcoat film 202 of thecounter substrate 200. The alignment films 113 do not exist at theportion the seal material 150 is formed. This is because the alignmentfilm 113 has a property of lowering the adhesion of the seal material150.

In FIG. 11, the alignment film 113 is optically aligned by UV-light at awavelength of 300 nm or less and the seal material 150 is cured byUV-light at a wavelength of 340 nm or more. At the time the sealmaterial 150 is to be cured, the optical alignment for the alignmentfilm 113 will already be finished. If the UV-Tight at a wavelength of300 nm or less is applied again to the alignment film 113 afterfinishing the alignment treatment, the alignment film 113 willdeteriorate.

The degradation can be prevented by filtering the UV-light for curingthe seal material 150 and use the UV-light that has been cut off thelight at a wavelength of 300 nm or less, or by using a UV-lightshielding mask to thereby prevent radiation of the UV-light to thealignment film 113. However, forming the filter for UV-light increasesthe manufacturing cost, and the filter has to be replaced frequentlybecause the UV-light deteriorates the filter. On the other hand, themethod of using the light screening mask involves the problem asdescribed herein earlier (refer to SUMMARY OF THE INVENTION).

The present invention described in the following by way of embodimentsprovides a configuration that can prevent UV-degradation of thealignment film without providing a filter for the UV-light light sourceand using a light shielding mask upon UV-curing of the seal material.

Embodiment 1

FIG. 1 is a cross sectional view showing the structure of a liquidcrystal display device of Embodiment 1. A cross sectional view of thedisplay region is shown on the left and a cross sectional view of theseal portion is shown on the right.

In FIG. 1, a TFT circuit 120 is formed over a TFT substrate 100. The TFTcircuit 120 collectively represents the configuration from the gateelectrode 101 to the inorganic passivation film 106 in FIG. 9. The sameapplies to the following drawings.

The device shown in FIG. 1 is a monochromatic liquid crystal displaydevice. Since the configuration of FIG. 1 is identical with that of FIG.11 except that a UV-light absorption layer 210, a feature of the presentinvention, is formed between each black matrix 201, detailed descriptionfor the structure is omitted. The arrow UV in FIG. 1 represents theUV-light for curing a seal member 150.

FIG. 2 is a flow of manufacturing of the liquid crystal display deviceof Embodiment 1. In FIG. 2, the manufacturing flow for the TFT substrate100 is shown on the left. Since the manufacturing process for the TFTsubstrate 100 has been described with reference to FIG. 9, detailsthereof are omitted. After an alignment film 113 is coated over the TFTsubstrate 100 and then baked, an alignment treatment is performed on thealignment film 113 by using UV-light. A wavelength of the UV-lighteffective for the alignment treatment is 300 nm or less.

Since the manufacturing process for the counter substrate 200 shown onthe right side of FIG. 2 has been described with reference to FIG. 9,its details are omitted. After coating and baking the alignment film113, an alignment treatment is performed upon the alignment film 113 byusing UV-light at a wavelength of 300 nm or less. Then, a seal material150 is formed on the counter substrate 200 and liquid crystals aredropped into the region surrounded by the seal material 150.

Next, the TFT substrate 100 and the counter substrate 200 are bonded bymeans of the seal material 150. As shown in FIG. 1, UV-light is radiatedon the counter substrate side to cure the seal material 150. A lightshielding mask is not used at this process. The seal material 150reacted and cured by UV-light at a wavelength of 340 nm or more,however, the UV-light used here includes not only UV-light at awavelength of 340 nm or more but also UV-light at a wavelength of 300 nmor less. In the conventional configuration, when the UV-light includesUV-light at a wavelength of 300 nm or less, the alignment film isdegraded if the seal material 150 is cured without using the lightshielding mask.

In the portion where a black matrix 201 is formed, the black matrix 210yields a light shielding effect against the UV-light. However, in theconventional embodiment, since only the overcoat film 202 is present atthe portions where the black matrices 201 are not formed, the UV-lightat a wavelength of 300 nm or less transmits the overcoat film 202. Inthis embodiment, a UV-light absorption layer 210 is formed between ablack matrix 201 and a black matrix 201 as to shield particularly theUV-light at a wavelength of 300 nm or less. Thus, degradation of thealignment film can be prevented without disposing a light shieldingmask.

FIG. 3 is a graph showing the UV-light transmittances of the organicmaterials used in the present invention: that is, the overcoat film 202(material for OC), the organic passivation film 107 (organic PASmaterial), and the UV-light absorption layer 210 (UV absorption layer)which are. As shown in FIG. 3, the transmittance of the UV-lightabsorption layer 210 is extremely low to UV-light at a wavelength of 300nm or less. On the other hand, the layer has a high transmittance toUV-light at a wavelength of 340 nm or more.

In FIG. 3, the transmittance of the UV-light absorption layer 210 to theUV-light at a wavelength of 300 nm is 10%, and the transmittance of theUV-light absorption layer 210 to the UV-light at a wavelength of 340 nmis 90%. The values represent those that can be obtained when theUV-light absorption layer 210 has a thickness of 1 μm. The table in FIG.4 shows the result of an evaluation of the transmittances in the displayregion and the seal portion of the liquid crystal display device shownin FIG. 1 to the UV-light at a wavelength of 300 nm and at a wavelengthof 340 nm, for the conventional example and the present embodimentprovided with the UV-light absorption layer 210, respectively.

FIG. 4 shows the intensity of the UV-light that were radiated from thecounter substrate 200 side, transmitted through the liquid crystaldisplay device, and then measured at the TFT substrate 100 side.

In FIG. 4, since the configurations of the seal portions 150 of theconventional example and this embodiment are same, the UV-lighttransmittance is identical. On the other hand, in the display portion,since the UV-light absorption layer 210 exists in this embodiment, whilethe transmittance to the UV-light at a wavelength of 300 nm is 2.7% inthe conventional example, it is lowered to 0.6% in this embodiment. Ascan be seen from FIG. 3, the transmittance to UV-light at a wavelengthof 300 nm or less is further lowered. Therefore, according to thisembodiment, since the UV-light at a wavelength of 300 nm or less thataffects the alignment film 113 scarcely transmits in the display region,the damage to the alignment film 113 due to the UV-light can beinhibited.

However, the transmittance to the UV-light at a wavelength of 340 nm is13.6% in the conventional example, whereas it increases to 19.9% in thisembodiment. This is because the UV-light absorption layer shows highertransmittance than that of the overcoat film 202 to the wavelength at awavelength of 340 nm or more. However, since the UV-light at awavelength of 340 nm or more causes no damage to the alignment film 113,practically there would be no problem.

The table in FIG. 4 shows examples. The film thickness of the UV-lightabsorption layer 210, etc. actually varies. The effect of the inventioncan be obtained even when the thickness of the UV-light absorption layer210 and other elements varies, so long as the transmittance to theUV-light at a wavelength of 300 nm or less in the display region is 1%or lower, and the transmittance to the UV-light at a wavelength of 340nm in the seal portion is 20% or higher.

Embodiment 2

FIG. 5 is a cross sectional view showing the structure of a liquidcrystal device of Embodiment 2. A cross sectional view of the displayregion is shown on the left and the cross sectional view of the sealportion is shown on the right. The configuration of FIG. 5 is differentfrom that of Embodiment 1 in FIG. 1 in that a UV-light absorption layer210 is formed instead of the overcoat film. In FIG. 5, the UV-lightabsorption layer 210 is formed not only in the display region but alsoin the seal portion instead of the overcoat film.

In FIG. 5, after the TFT substrate 100 is bonded to the countersubstrate 200 by means of the seal material 150, a UV-light is radiatedfrom the counter substrate 200 side to cure the seal material 150 in thesame manner as performed in Embodiment 1. Further, in this embodiment, alight shielding mask for preventing radiation of the UV-light to thedisplay region is not used as with Embodiment 1.

The transmittance of the UV-light absorption layer 210 and the overcoatfilm 202 to UV-light is as shown in FIG. 3. The UV-light absorptionlayer 210 has a lower transmittance to UV-light at a wavelength of 300nm or less and shows a higher transmittance to UV-light at a wavelengthof 340 nm or more compared with the overcoat film 202. Accordingly, evenif the UV-light is radiated without using a light shielding mask, onlyan extremely small amount of the UV-light at a wavelength of 300 nm orless reaches the alignment film 113 in the display region. The effect ofthe UV-light on the alignment film present in the display region isextremely small.

The table shown in FIG. 6 compares the transmittances of UV-light at awavelength of 300 nm and UV-light at a wavelength of 340 nm in thedisplay portion and in the seal portion of this embodiment andEmbodiment 1 and the conventional example. The measuring method issimilar to that taken for the measurement for FIG. 4, the UV-light isradiated from the counter substrate 200 side and the degree oftransmittance of the UV-light are measured at the TFT substrate 100 sideand compared.

In the seal portion 150, different from the conventional example andEmbodiment 1, the UV-light absorption layer 210 is formed instead of theovercoat film 202 in this embodiment. While the transmittance to theUV-light at a wavelength of 300 nm is as low as 2.7%, the transmittanceto the UV-light at a wavelength of 340 nm is as high as 49.2%. That is,since the UV-light at a wavelength of 340 nm for curing the sealmaterial 150 is less absorbed by the UV-light absorption layer 210, theseal material is irradiated efficiently with the UV-light. Therefore,the seal material 150 can be cured efficiently by the UV-light in thisembodiment.

In the display region, regarding the UV-light at a wavelength of 300 nm,since the overcoat film 202 is entirely replaced by the UV-lightabsorption layer 210, the transmittance is more lowered than that ofEmbodiment 1, to 0.2%. Accordingly, since the UV-light at a wavelengthof 300 nm is cut off more efficiently in this embodiment, damage to thealignment film 113 can be prevented more efficiently. Although thetransmittance to the UV-light at a wavelength of 340 nm in the displayregion is as high as 49.2%, the effect caused by the UV-light at awavelength of 340 nm on the alignment film is small, so it does notdamage the alignment film 113.

As described above, the seal material 150 can be cured by UV-lightwithout damaging the alignment film 113 even when a light shielding maskis not used in this embodiment as well.

As shown in FIG. 5, in this embodiment, a columnar spacer 130 is formedon the UV-light absorption layer 210. By using the same material as theUV-light absorption layer 210 for the columnar spacer 130, the UV-lightabsorption layer 210 and the columnar spacer 130 can be formedsimultaneously.

As an example of this process, a UV-light absorption layer of athickness equal to the total thickness of the UV-light absorption layer210 and the columnar spacer 130 is coated over the counter substrate200. Then, only the portion other than the columnar spacer 130 isremoved by etching to a predetermined thickness by controlling theexposure dose in photolithography. The columnar space 130 and theUV-light absorption layer 210 can thus be formed simultaneously in theprocess of forming the columnar spacer 130, resulting in a reducedmanufacturing cost.

Embodiment 3

FIG. 7 shows a cross sectional view of a liquid crystal display deviceof Embodiment 3 according to the invention. Different from Embodiment 1and Embodiment 2, the device shown in FIG. 7 is a color liquid crystaldisplay device. Color filters 220 are formed between each black matrix201 in the counter substrate 220. On the other hand, in the TFTsubstrate 100, a UV light absorption layer 210 is formed instead of anorganic passivation film 107. Since other portions have the sameconfiguration as those of Embodiment 1 in FIG. 1, descriptions thereofare omitted.

In this embodiment, a counter substrate 200 having an optically alignedalignment film 113 and a TFT substrate 100 having an optically alignedalignment film 113 are sealed at their periphery with a UV-curable sealmaterial 150. As shown in FIG. 7, UV-light for curing the seal material150 is radiated from the TFT substrate 100 side. The relationship of theUV-light transmittances of the organic passivation film 107 and theUV-light absorption layer 210 are as shown in FIG. 3. That is, theUV-light absorption layer 210 efficiently cuts off the UV-light at awavelength of 300 nm or less, and it efficiently transmits the UV-lightat a wavelength of 340 nm or more, compared with the organic passivationfilm 107.

In the configuration shown in FIG. 7, when UV-light is radiated from theTFT substrate 100 side, since the UV-light absorption layer 210 isformed instead of the organic passivation film 107 at the TFT substrate100 side, UV-light at a wavelength of 300 nm or less which may damagethe alignment film 113 is efficiently cut off in the display region.Although UV-light at a wavelength of 340 nm or more is more likely totransmit through the UV-light absorption layer 210 in the displayregion, the UV-light at a wavelength of 340 nm or more does not damagethe alignment film 113, so there is no problem.

On the other hand, for the seal material 150 at the seal portion, sincethe UV-light absorption layer 210 formed over the TFT substrate 100 hashigher transmittance to the UV-light at a wavelength of 340 nm or more,the seal material 150 can be cured efficiently. While also the UV-lightat a wavelength of 300 nm or less is less radiated to the seal material150, the UV-light within this range causes less effect on the curing ofthe seal material. Thus, no problem arises.

As described above, the seal material 150 can be cured by UV-light withno damage on the alignment film 113 due to the UV-light radiationwithout using a light shielding material in this embodiment as well.

Embodiment 4

FIG. 8 is a cross sectional view of a liquid crystal display deviceshowing Embodiment 4 of the invention. The device shown in FIG. 8 isalso a monochromatic liquid display device as with those of Embodiment 1and Embodiment 2. In FIG. 8, a UV-light absorption layer 210 is formedbetween each black matrix 201 as in Embodiment 1. On the other hand, aUV-light absorption layer 210 is formed instead of an organicpassivation film 107 at the TFT substrate 100 side as with Embodiment 3.That is, this embodiment has a configuration such that the UV-light at awavelength of 300 nm or less is efficiently cut off at both the countersubstrate 200 side and TFT substrate 100 side, and the transmittance tothe UV-light at a wavelength of 340 nm or more is high also at bothsides.

In this embodiment; UV-light can be radiated from both the countersubstrate 200 side and the TFT substrate 100 side as shown in FIG. 8.Since it is adapted such that the UV-light at a wavelength of 300 nm orless is efficiently cut off at both the counter substrate 200 side andthe TFT substrate 100 side, the UV-light does not damage the alignmentfilm 113.

On the other hand, the UV-light at a wavelength of 340 nm or higher istransmitted efficiently, particularly in the TFT substrate 100 side.Further, also in the counter substrate 200 side, the transmittance ofthe seal portion 3 to the UV-light at a wavelength of 340 nm or more ismaintained at a level equivalent to that of the conventional example.

Therefore, according to this embodiment, since the radiation dose of theUV-light at a wavelength of 340 nm or more to the seal material 150 canbe increased remarkably, the seal material 150 can be cured by UV-lightwithin a shorter time period. Further, the seal material 150 can becured by UV-light with no damage to the alignment film 113 without usinga light shielding mask as with Embodiment 1 to 3.

1. A liquid crystal display device comprising: a TFT substrate having analignment film; a counter substrate having an alignment film, thecounter substrate being bonded to the TFT substrate by means of a sealmaterial; and liquid crystals sealed inside the substrates and the sealmaterial; wherein a UV-light absorption layer is formed between eachblack matrix, the black matrices and the UV-light absorption layer beingcovered by an overcoat film, the overcoat film being covered by thealignment film; the seal material is a UV-light curable resin; and thetransmittance of the UV-light absorption layer to UV-light at awavelength of 300 nm is lower than that of the overcoat film, and thetransmittance of the UV-light absorption layer to UV-light at awavelength of 340 nm is higher than that of the overcoat film.
 2. Aliquid crystal display device comprising: a TFT substrate having analignment film; a counter substrate having an alignment film, thecounter substrate being bonded to the TFT substrate by means of a sealmaterial; and liquid crystals sealed inside the substrates and the sealmaterial; wherein a UV-light absorption layer is formed between eachblack matrix and over the black matrices, and the alignment film isformed over the UV-light absorption layer; the TFT substrate is coveredby a TFT circuit and an organic passivation film covering the TFTcircuit, and over the organic passivation film, counter electrodes, aninterlayer insulation film, and pixel electrodes are formed in thatorder, or in the order of the pixel electrodes, the interlayerinsulation film, and the counter electrodes; the alignment film isformed over the pixel electrodes or the counter substrate; the sealmaterial is a UV-light curable resin; and the transmittance of theUV-light absorption layer to UV-light at a wavelength of 300 nm is lowerthan that of the organic passivation film, and the transmittance of theUV-light absorption layer to UV-light at a wavelength of 340 nm ishigher than that of the organic passivation film.
 3. A liquid crystaldisplay device comprising: a TFT substrate having an alignment film; acounter substrate having an alignment film, the counter substrate beingbonded to the TFT substrate by means of a seal material; and liquidcrystals sealed inside the substrates and the seal material; wherein acolor filter is formed between each black matrix, the black matrices andthe color filters being covered by an overcoat film, the overcoat filmbeing covered by the alignment film; the TFT substrate is covered by aTFT circuit and a UV-light absorption layer covering the TFT circuit,and over the UV-light absorption layer, counter electrodes, aninterlayer insulation film, and pixel electrodes are formed in thatorder, or in the order of the pixel electrodes, the interlayerinsulation film, and the counter electrodes; the alignment film isformed over the pixel electrodes or the counter substrate; the sealmaterial is a UV-curable resin; and the transmittance of the UV-lightabsorption layer to UV-light at a wavelength of 300 nm is lower thanthat of the overcoat film, and the transmittance of the UV-lightabsorption layer to UV-light at a wavelength of 340 nm is higher thanthat of the overcoat film.
 4. A liquid crystal display devicecomprising: a TFT substrate having an alignment film; a countersubstrate having an alignment film, the counter substrate being bondedto the TFT substrate by means of a seal material; and liquid crystalssealed inside the substrates and the seal material; wherein a UV-lightabsorption layer is formed between each black matrix, the black matricesand the UV-light absorption layer being covered by an overcoat film, theovercoat film being covered by the alignment film; the TFT substrate iscovered by a TFT circuit and a UV-light absorption layer covering theTFT circuit, and over the UV-light absorption layer, counter electrodes,an interlayer insulation film, and pixel electrodes are formed in thatorder, or in the order of the pixel electrodes, the interlayerinsulation film, and the counter electrodes; the alignment film isformed over the pixel electrodes or the counter substrate; the sealmaterial is a UV-curable resin; and the transmittance of the UV-lightabsorption layer to UV-light at a wavelength of 300 nm is lower thanthat of the overcoat film and that of the organic passivation layer, andthe transmittance of the UV-light absorption layer to UV-light at awavelength of 340 nm is higher than that of the overcoat film and thatof the organic passivation layer.
 5. A liquid crystal display deviceaccording to claim 1, wherein: the seal material is a UV-curable resinthat is cured by UV-light at a wavelength of 340 nm or more; and thealignment film is optically aligned by UV-light at a wavelength of 300nm or less.
 6. A liquid crystal display device according to claim 2,wherein: the seal material is a UV-curable resin that is cured byUV-light at a wavelength of 340 nm or more; and the alignment film isoptically aligned by UV-light at a wavelength of 300 nm or less.
 7. Aliquid crystal display device according to claim 3, wherein: the sealmaterial is a UV-curable resin that is cured by UV-light at a wavelengthof 340 nm or more; and the alignment film is optically aligned byUV-light at a wavelength of 300 nm or less.
 8. A liquid crystal displaydevice according to claim 4, wherein: the seal material is a UV-curableresin that is cured by UV-light at a wavelength of 340 nm or more; andthe alignment film is optically aligned by UV-light at a wavelength of300 nm or less.